Subsea power line communication is a special form of underwater communication. It is preferably used in exploring and exploiting gas and oil fields located at the seabed. Subsea communication is used, for example, for transmitting various data between topside control sites and subsea wellheads. Gas and oil fields that are explored or exploited using electronic communication to the wellheads or to other electronic equipment are sometimes called “electronic fields” (e-fields).
In prior art, different techniques for subsea communication have been described. On the one hand, there are wired electric or optical connections, on the other hand there are wireless connections. The wired connections can be subdivided into a first group providing communication lines for electronic or optical connections separate from electric power lines, and a second group utilising power lines for electronic communications. In the latter case, advantageously no separate communication lines are needed.
For example, in US 2005/0243983 A1, a modem for receiving and transmitting data from and to a conductor is described. It comprises an output drive for transmitting data to the conductor, a receiver for receiving data from the conductor and impedance matching means for matching an impedance of a receiver input with an impedance of the conductor. A gain of the output drive, a receiver gain and the impedance of the receiver input are adjustable at this modem.
Modems typically use a printed circuit board (PCB) onto which electronic components such as integrated circuits (IC) are mounted. These components usually are sensitive to electro-magnetic radiation, in particular to radiation in the radio frequency (RF) range, resulting in electronic interference and noise. As a consequence, the bit rate and the operational range of a modem connection are affected by the extent of radiation its electronic components are exposed to. The negative impact of radiation is even increased as the tracks connecting the electronic components act as receiving aerials. Therefore, the electronic components and the printed circuit board are sought to be shielded against radiation.
The known modems for subsea power line communication use a metal box that entirely surrounds their printed circuit board to shield the electronic components and the tracks between them from external radio frequency radiation. However, the possible bit rate and the possible operational range of these modems is limited because of the limited shielding properties of the metal box encapsulation.